Glass-like Thermal-Transport in Symmetry-Broken Clathrates

TL;DR

This paper explains the glass-like thermal conductivity behavior in symmetry-broken type-I clathrates by emphasizing the role of dipole-dipole interactions among off-centered guest ions, providing a quantitative interpretation.

Contribution

It introduces a model highlighting dipole-dipole interactions as key to understanding thermal transport in symmetry-broken clathrates, aligning with experimental observations.

Findings

Dipole-dipole interactions are crucial for reproducing thermal conductivity characteristics.

The model explains differences in thermal conductivity between p-type and n-type β-BGS.

Quantitative agreement with experimental data supports the proposed mechanism.

Abstract

We present the quantitative interpretation for the glass-like behavior of thermal conductivities $\kappa(T)$ for type-I clathrate compounds involving off-centered guest ions. It is shown that the dipole-dipole interaction generated in cage/guest-ion systems is crucial to reproduce the characteristics of thermal conductivities for these symmetry-broken clathrates. The above scenario also explains well the difference of $\kappa(T)$ between the $p$-type and the $n$-type $\beta$-BGS found recently by K. Suekuni et al. [Phys. Rev. B, 77 (2008) 235119.]